In a heat exchanger such as a radiator, an oil cooler and an intercooler (outer cooler), a heat exchanger structured to prevent air accumulation therein has been typically known (Patent Literatures 1 and 2).
Patent Literature 1 discloses a water-cooled intercooler. The water-cooled intercooler is structured such that a cross-sectionally arc-shaped groove bulging upward is provided on an upper surface of a casing into which cooling water flows and air in the casing is guided to a cooling-water inlet via the groove to be discharged outside from the cooling-water inlet.
Patent Literature 2 discloses a horizontal-flow type oil cooler. The oil cooler is structured such that a gap between a cap of a header pipe and a tube is made small so as to keep air from remaining in the header pipe, whereby air pool is not substantially generated in the gap.